Radio detector system



arch 19, W35. H. c. 'DUFT 1,994,506

RADIO DETECTOR SYSTEM Filed Dec.. 15, 1930 3 Sheets-Sheet l March 19, 1935. H. c. DUFT 1,994,506

RADIO DETECTOR SYSTEM Filed Dec. 15, 1930 s sheets-sheer 2 9/ IMIIIIIII a4 v T /fl! |||||||I} w fizz/6725;?

ch 19, 193. H. c. DUFT I 1,994,506

' RADIO DETECTOR SYSTEM Filed Dec. 15. 1939 3 Sheets-Sheet 5 fizz/522237 Patented Mar. 19, 1935 STAT Es PA'FENT I 1,994,506 :Immo DETECTOR SYSTEM" Harry 0. hurt, Chicago, Illi, assilgnor in western Electric Company, Incorporated, New York, N; Y., a corporation of New York Application; December 15, l930l scrial No; 502,326

' invention relatesito a radio circuit and moreparticula'rly to a circuit and apparatus for detecting! radio frequency signals.

Detector systems in common use today rely' upon'lthe" gridcurrent-of" an audion or upon the asymmetric characteristics of an audion, whereby one side of a radio frequency wave is amplifled to a greater'degreethan the'other to obtain rectification. This results in low amplification the detector stage of the receiver and poor rectification since the detector audion is called uponto perform two'functions', namely rectific'a tiers and amplification; the'best conditions for one of which are diiferent than forthe other.

An" object of my invention" is to provi'deanew and improved detector circuit. -5 Y A furth'er object is to provide a rectifier associated with the anode circuit of an audion.

A turth'er object isto provide a full wave de- 2o; tectora 1 r Other objects and advantages will appear as the: description proceeds. Refrringto thedr'awin'gs, V

1' is a diagrammatic illustration ofem -embodying-my invention, and

a cir Figs; 23 3, 4; 5', dds illustrate modified forms oflthe -invefitien; 7

The circuit shown in Figz 1* includes a-Qthermimic-device or audion 5 having a tunedradio- 3oz frequency input circuit comprising a; transformer 6-- and variable condenser; 7*. The thermionicdvicefi has the usual grid=8', p1ate or*anode 9} and an indirectlyheated cathode 1 1;. The anode cir cuitofi'thethermionic device includesa suitable" impedance such as aresistanceelement 12 and a sdurceof energy illustrated 'for convenience as a" hatdie'ry 1 3i The negative side of' the battery i's prefrablygrounded at 14 and a re'sistance '15" and hy-passcondenser ldare provi'ded tonegatively'bias the grid 8 relativeto cathode 11'.

It is e'vide'nt that when a: constant current is flowing n the anode Circuit'pthat is; whenno signal is impressed" upon the grid} the point 17 andv a point 18 of the source 13Ywi-11" be'atequal: potentials? A rectifierof any suitable type such as a crystal or athermionic rectifier, I9- is connecte'd across these points. Rectifier 19- consists the radio'frequency wave.

' has a radio frequency transformer 4'2' and' a'v When an alternating current is impressed grid: 8; point 17-wi11 alternately tend tdbecofiie positive and negative with: respect to point 18';

however; on account of rectifier 19, one side ofthe? alternating current wave will be eliminated. The 5 other side of the alternating current wave" will be; imiofressed through condenser 23 upon the grid-1 24- of a thermionic device 25; Condenser" 2-3 merely serves-to prevent-the high potent 1' of.sour'ce -13 fi Qm'reachinggridM (if-device 2'5. 10

Thermionic device 25- hasin addition to giid 24 an anode-26, and: an indirectly heated cathode" 27" and. serves to amplify the rectified radid'f quency signals supplied thereto; The mode 0 and a filter circuit havinga radio frequencs choke co'il- 29and filter condensers'fi'l. 1! source of energy-'32 is connectedat one side' to tra" former 28 and grounded cnthe' other-"side a t 33L 'I hecathode lead of this-deVice-Has-a-bi ing 'resistor 34 and bypass condenser 35 similar to thatof device 5;

It will be noted that'- the load 'on tliri'ni'oni device 25"is redu'ced to 'substantially onea 'f" What it would be if one side'bf the reg-die re quencyrwave were not eIimir'Iatedjin-the preceding stage; Thus, a greater amplification of useful radio-frequency energymayhe hadWitHodtdVr" lo'ading a last-radio frequencyamplifier audi Whi1e' itwas-stated that'th'pointm m a'djhste'd to render points-17-' anc1="I8 equipote tiaig itf may" be advantageous in-some case we bias one point" with" respect to the other, as for instance the radio frequencywave iii-not modulated onehun'dred percent.-

Fig; 2'- represents' a modified form of the vention operating uptnsomewnatme'same innat mentalprinciple, but enteringm gine; ini siorn(a details: The input 01' grid circuit of audion 1' riable 'tu'ning condenser 'I'he'anod me 15'- includes a'resistance element--44; a source of en erg-y 45Fa-nd a biasing "resistance"46 and b pfass' 'conden'ser i'fi- The negativeside of so'ii'r 45 is preferabiy grounded at 48'.- when no 'sig poi tential s imbrssed 011" the grid of ai'ldioh i l pbints 4=9 ahd fil will b at equal potentials? C511- n'ectedf across hese points i's-a-rectifiei' 5 2"ha v-- ing are'sistanca 53'- iniseries therewith; The I ohmic vaiue of resistance 53 i's preferably-rather higher the order-"ofan ordinary idlea'k re canned: d

Seance? output conductor 5'4 to-apoin-t 55between rectifier 52am esist It eVidnfithata-radib fre uency sig a negative with respect to point 49. When point 51 is negative with respect to point 49, no current will flow through the rectifier or resistance 53 and point 55 will be of the same potential as point 49. However, when point 51 becomes positive with respect to point 49, current will fiow through the rectifier and resistance 53 and vary the potential of point 55 with respect to point 49. If the resistance 53 is given a large value, only a small amount of current will be required through the resistance to bring point 55 to substantially the same potential as point 51. An output conductor 54 is connected to point .55 and leads through condenser 56 to the grid of an audion 57; A resistance 58 is preferably connected from the'grid of audion 57 to ground. The anode circuit of audion 57 includes a filter circuit'59, audion-transformer 61, source of energy 62, and abiasing resistance 63 by-passed by a condenser 64. The unidirectional radio frequency signal is impressed" upon thegrid of audion 57 and is amplified and the amplified output of this audion is filtered and passed through the primary of audio transform- Fig. 3 illustrates the system of Fig. 2 adapted for full wave detection, audion65 is a radio frequency amplifier and has anv impedance 66 in its anode. circuit. A' pair of resistances 67 and 68 are connected from a conductor 69 which connects the anode of audion 65 to impedance 66 and to a substantially equipotential point '71 .of a source of energy72. Between the resistances 6'7 and 68. the conductor 69 are valves 73 and '74 respectively, which are connected in.opposite directions. Output conductors '75 and 76 are connected to points Tl-and 78 and lead the rectified currents to grid '79 and cathode 81 of an audion 82 respectively. Thus both halves of thecycle of the radio frequency wave are impressed cumulatively on the input. circuit of audion 82 and are amplified in the anode circuit, which contains afilter system 83 for converting the high frequency impulses to audio frequency. The audio frequency current is applied to the primary of an audio transformer 84. 7 r

Fig. 4 illustrates a detector system consisting of a radio frequency amplifying audion 91 having an impedance 92 in its output circuit, which is connected to audion 91 by a conductor 93. Connected to conductor 93 is a full wave rectifier tube having indirectly heated cathodes 94 and 95. and anodes 96 and 97.. ,The elements 94 and 96 may be placedin a separate envelope from elements 95 and 9 7, or if; placed in the same envelope they should be spaced as far apart as convenient to avoid interference with each other. Cathode 94 is connected-to conductor :93 and anode 96 is connected to an output circuit having parallel condensers 98 and 99 grounded at 101, and .a radio frequency choke 102 in series between them. In the other valve ofthe rectifier, anode 9'? is connected to conductor 93 and cathode 95 isconnected to the other side of the output cir cuit having parallel condensers 102 and 103 also grounded at 101 and a radio frequency choke 104' in,series-between them. The output circuit also includes the primary of an audio transformer 105-. The operation ofthis circuit is as follows: Assuming that a voltageof 180 volts is applied to the anode circuit of audion 91 and that the impedance value of the'audion and impedance 92 are sorelated'that conductor 93 has a potential of 90 volts when no signal :is. impressed on the grid of the audion, the condensers 98, 99, 102 and 1,994,506 103 will thenbe charged to a potential of 90 volts through elements 95 and 9'7. If now a signal is impressed on the grid of audion 91 and the 7 grid becomes negative, the potential of conductor 93 will rise to a value of, let us assume 90 plus 3. Condenser 102 will then be charged to .the'

value of 90 plus 3 volts through elements 95 and 97. If the gridthen becomes relatively positive on the other half of the cycle,fthe potential of.

conductor 93 will fall to a valued 90 minus 3 on condensers 102 plus 98 will then equalize by a flow of current through the primary of the audio. l transformer and the following cycle of the radio.

supplied to the audio transformer. r

Fig. 5 illustrates-a modification of the circuit of Fig 4. 'The input circuit of audion may be of anysuitable type and the output circuit of detector. audion 111 may be similar .to'that off. I

Fig.4 and the description thereof is therefore,

not repeated. Detector audion, 111 has apair .of

cathodes 1'12 and 113, one connectedto conductor:

114 andthe other to the conductor 115 leading to the filter circuit, a plate or anode 116, pref-i erably of the 'mesh type surrounds each of the cathodes, one of the plates being connectedgto. conductor '114;and the other to conductor: 117.5 leading to the other side of the filter circuits Grids 118 cooperatewith the cathodes and plates to increase the electron flow from the cathodes to the plates when the plates become positive relative to their respective cathodes. A battery119 1, is connected with its negative side. to cathode 112,

and its positive side to one of the grids to maintain the grid positive with respect to cathode 112,, and a similar battery 120 is connected with its negative side to cathode 113 and its positive. side to the other grid. 7

Fig. 6 illustrates a circuit similar to that bf. rig.

5, except that batteries 119 and 120 are replaced by a circuit permitting the audion 110i. anddetector audion 111' to be operated fromv a single source of energy 121. ,An impedance 122--is connected to cathode 112' and'a similarimpedance,

ends and connected to anoint 129 of source-121.

at a higher potential thanpoint 128. Thus the grids willbe maintained at a higher potential than the cathodes causing a large-number of electrons toflow from the cathodes to the-plates whenever one ofthe plates becomes pos evegwign? respect to its cathode- WhatI claim as new and desire to protect. by Letters Patent" of the Unitedstates isz 1. Ina radiosystem, an a dion, an anodejcir-i cuitfor said audiom including an impedance and a source of energy, .and a rectifier connected across normally .equipotential Q'pdints 'ini said anodecircuit. Y

M 2. Ina radio system, an audion; anode'fcifl' cuit including animpedance and a source of .en

ergy, a rectifier having, anode and; cathodeelej-j merits, one of said' elements beingconnectedjo a point between the anode and impedance and means connected to the other element for im-' said anode circuit, and an output conductor connected between said series rectifier and impedance.

4. In a radio system, an audion, an anode circuit including an impedance and a source of energy, a rectifier connected to a point of fluctuating potential in said anode circuit, the other side of the rectifier being connected to an impedance in series with said rectifier, means for applying a potential to the opposite end of said series impedance, which is substantially equal to the normal potential of said point, and an output conductor connected between the rectifier and said series impedance.

5. In a radio system, an audion, an anode circuit, including an impedance, a pair of rectifiers oppositely connected to a point of fluctuating potential in said anode circuit, an audio circuit having one side connected to one of said rectihers and the other side to the other rectifier, and capacitive means in said audio circuit for receiving energy from said rectifiers.

6. In a radio system, a circuit, means for causing a constant and superposed fluctuating current to flow in said circuit, a pair of rectifiers oppositely connected at one side to a point of fluctuating potential in said circuit, and an output circuit connected to the other sides of said rectifiers and having capacitive means for receiving current impulses from said rectifiers.

7. In a radio system, a full wave detector comprising an audion, an anode circuit, a pair of rectifiers connected to a point of fluctuating potential in said anode circuit, one of said rectifiers being connected inversely with respect to the other, an impedance in series with each of said rectifiers, means connected to the other ends of the impedances for applying a constant potential to the other ends of said impedances, and output conductors connected between the rectifiers and impedances.

8. In a radio system, an audion, an anode circuit therefor, including an impedance and a source of energy, a pair ofirectifiers connected to a point of fluctuating potential in said circuit, one of said rectifiers being inversely connected with respect to the other, an impedance in series with each of said rectifiers, means connected to the other ends of the impedances for applying a potential to the other end of said impedances, a second audion having a grid and cathode in its input circuit, a pair of conductors connected between said rectiflers and impedances, one of said conductors being connected to the grid of the second audion and the other being connected to the cathode.

, 9; In a radio system, an audion, an anode circuit therefor, including an impedance, and a rectifier connected across normally equipotential points in said circuit, one of said points being so chosen as to have a substantially constant potential when the impedance of the audion is varied, the other point being so chosen as to have a varying potential when the impedance of the audion is varied.

10. In a radio system, an audion, an anode circuit therefor, including an impedance and a. source of energy, a pair of rectifiers connected to a point of fluctuating potential in said anode circuit, a transformer having its primary circuit connected to said rectifiers, and a grounded condenser connected in parallel with respect to said transformer primary in each lead between the rectifiers and transformer primary.

11. In a radio system, an audion, an anode circuit for said audion including an impedance and a source of energy, a rectifier connected across normally substantially equipotential points in said anode circuit, and an output circuit connected to one of said points.

HARRY C. DUFT. 

